package com.mcg.ash;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.nio.MappedByteBuffer;

import java.nio.channels.FileChannel;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

public class MD5Util {
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9','a', 'b', 'c', 'd', 'e', 'f' };

    protected static MessageDigest messagedigest = null;

    static{
        try{
            messagedigest = MessageDigest.getInstance("MD5");

        }catch(NoSuchAlgorithmException nsaex){
            System.err.println(MD5Util.class.getName()+"初始化失败，MessageDigest不支持MD5Util。");

            nsaex.printStackTrace();

        }

    }

    public static String getFileMD5String(File file) throws IOException {
        FileInputStream in = new FileInputStream(file);

        FileChannel ch = in.getChannel();

        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());

        messagedigest.update(byteBuffer);

        return bufferToHex(messagedigest.digest());

    }

    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());

    }

    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);

        return bufferToHex(messagedigest.digest());

    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);

    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);

        int k = m + n;

        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);

        }

        return stringbuffer.toString();

    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];

        char c1 = hexDigits[bt & 0xf];

        stringbuffer.append(c0);

        stringbuffer.append(c1);

    }

    public static boolean checkPassword(String password, String md5PwdStr) {
        String s = getMD5String(password);

        return s.equals(md5PwdStr);

    }

    public static void main(String[] args) throws IOException {
        long begin = System.currentTimeMillis();


        File big = new File("C:\\ash\\wechat\\WeChat Files\\zhangfan9057\\FileStorage\\File\\2021-07\\LICChinaUnicomFDDDBS3900_V100R016_20210126K4LD6T.xml");

        String md5=getFileMD5String(big);

        long end = System.currentTimeMillis();

        System.out.println("md5:"+md5+" time:"+((end-begin)/1000)+"s");

    }

}

